青藏高原与黄土高原交错带天然草地群落特征及退化过程研究--以甘肃省白银市为例

对地处青藏高原与黄土高原交错带的白银市天然草地植物区系组成、草地类型结构以及退化草地物种数、生活型构成、盖度、生物量等植被特征进行了系统调查与分析．研究了不同退化演替时期草地群落结构特征的空间变化规律。结果表明：随草地退化程度的加剧，高位芽植物最先消失，草地植物群落物种数和优势种密度急剧下降，群落盖度、生物量比、鲜草产量与可食草产量百分数均呈逐渐下降趋势。提出了保护草地生态环境的思路。

Study on the Degrading Process and Character of Community of Natural Grassland in Crisscross Part of Qinzang and Loamy Plateau--Taking Baiyin City of Gansu Province as an Example

The constitution of the flora, type and structure of the grassland, plant amount and the vegeta tion coverage and biomass on the degraded grassland in Baiyin City of Crisscross Part of QinZang and Loamy Plateau were studied and analyzed. The varying regularity in space of structure and character of vegetation in different degrading period on nature grassland was also studied. With the severity of degeneration of grassland, from initial stage to latter period, the plant in perch-bud first disappeared, the plant amount of vegetation community and the density of predominant plant were declined sharply. The conver age, biomass and the proportion of the yield fresh grass to edible grass have also declined rapidly. In the end, the way was suggested in order to protect ecologic environment on natural grassland.